Traveling wave tubes (TWT) are used in various wireless devices including radar systems, satellite communications systems, wireless transponders of microwave backhaul links, etc. A TWT is a vacuum electronic device that acts as a microwave amplifier capable of providing a high gain and high output power. To accomplish this, TWTs use slow-wave structures that support the propagation of an electromagnetic (EM) wave and also accommodate the propagation of an energetic electron beam from within the device. The interaction between the electron beam and the EM wave results in amplification of the EM wave and a consequent boost in the amplitude of the EM wave thereby increasing the output power of the device. The gain of the device is a function of the interaction impedance and the total current of the electron beam, which is limited by the maximum dimensions of the slow-wave structure. As frequency increases, the dimensions of conventional slow-wave structures used in conventional TWTs decrease.